412 The Rev. W. D. Conybeare on M. de Beaumont's Theory 



refer the primary elevation of the transition rocks to a period 

 antecedent to the formation of the carboniferous lime. The 

 general direction of these transition lines of elevation is 

 E.N.E. and W.S.W., and they appear to have been attended 

 with great transverse fractures, which have often indicated 

 the course of the actual valleys. 



In the Island of Anglesea the whole of the transition chains 

 are highly inclined and much disturbed, while the old red sand- 

 stone, mountain lime and coal repose on their edges in nearly 

 horizontal strata. The lines of direction are here N.E. and 

 S. W. : this is also the general line of the transition chains of 

 North Wales. To this direction it is evident that the line of 

 the border of carboniferous limestone on the north, proceed- 

 ing from Ormes Head, is entirely unconformable. The same 

 N.E. and S.W. direction seems to prevail also in the transi- 

 tion chains of South Wales, while the lines of elevation of the 

 incumbent coal-measures range E. and W. ; and in the Vale 

 of Towy, while we find the transition rocks on the northern 

 bank nearly vertical, the carboniferous limestone chains on 

 the south do not deviate above 10° from being horizontal. 

 The general range of the transition chain occupying the pen- 

 insula of Devon and Cornwall ranges also from N.E. to S.W. ; 

 but here we have scarcely any opportunity of ascertaining 

 the relative position of those rocks as regards the carboni- 

 ferous series, for the overlying mantle of new red sandstone 

 is the only rock we observe in contact with their exterior 

 border ; unless, indeed, the limestone of Torbay, as Mr. De la 

 Beche has stated, be carboniferous. But this district appa- 

 rently has been subject to local convulsion at a much later 

 period, from the intrusion of greenstone dykes, so as to afford 

 no precise indications as to the general structure. 



The general parallelism of these transition chains, all nearly 

 ranging E.N.E. and W.S.W., is, as Elie de Beaumont has 

 well urged, very favourable to his theory: he classes this as 

 his first system, including the continental chains of the 

 Hundsruck. 



In conclusion, I would inquire whether we are to refer this 

 general direction of the Cornubian transition chain to the 

 eruption of the granitic masses which are constantly protrud- 

 ing through its axis. In this case we must refer that eruption 

 to a period so late as to include almost* the whole series of 

 transition rocks which appear to be equally effected by it. 



I have much preferred in this essay the endeavour to 



* De Beaumont has, however, considered its precise Eera to have been 

 anterior to the formation of the more recent members of the transition 

 series, such as the transition limestones of Dudley, Malvern and Wenlock 

 Edge. 



